/*
 * Copyright 2018-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.gateway.rsocket.filter;

import reactor.core.publisher.Mono;

/**
 * Contract for interception-style, chained processing of Web requests that may be used to
 * implement cross-cutting, application-agnostic requirements such as security, timeouts,
 * and others.
 *
 * Copied from WebFilter
 *
 * @author Spencer Gibb
 */
public interface RSocketFilter<E extends RSocketExchange, FC extends FilterChain<E>> {

	/**
	 * Enum to signal successful end of chain reached without the end being empty, i.e.
	 * Mono&lt;Void&gt; via Mono.empty(). This is because at the end of the chain an
	 * actual value needs to be returned. We can map success, but not empty.
	 */
	enum Success {

		INSTANCE

	} // should never have more than one value

	/**
	 * Process the Web request and (optionally) delegate to the next {@code RSocketFilter}
	 * through the given {@link FilterChain}.
	 * @param exchange the current RSocket exchange
	 * @param chain provides a way to delegate to the next filter
	 * @return {@code Mono<Success>} to indicate when request processing is complete.
	 */
	Mono<Success> filter(E exchange, FC chain);

}
